Wave generating system



APril 27, 1943--` E. PETERSON 2,317,482

WAVE GENERATING SYSTEM Filed Dec. 5l, 1941 S TURABLE MAGNET/c come co/L F/G- 2 Patented Apr. 27, 1943 WAVE GENERATING SYSTEM Eugene Peterson, New York, N. Y., assigner to Bell Telephone Laboratories, Incorporated, New York, N. Y., a corporation of New York Application December 31, 194i, serial No. 425,087

17 Claims.

The invention relates to the generation of alternating current waves and particularly to the generation of a number of alternating current waves of dierent frequencies from a single wave of a given frequency.

In certain carrier communication systems it is required to have two different groups of carrier/frequencies with a wide frequency spacing between the groups, all frequencies in both groups being different harmonics of the same for a carrier communication system of the abovefundamental frequency, and it is usually satisfactory for the group of higher frequencies to be at a lower power level than the lower group of carrier frequencies. It is known how to employ for the carrier supply in such a system a harmonic generator of the type providing a range of harmonics extending from a low harmonic to a high one with the amplitudes of the harmonics decreasing gradually as their frequency position in the harmonic scale increases. y

An object of the invention is to produce in systems of theV above-described type the required range of harmonics at the desired power levels -emciently and economically.

This object is attained in accordance with the Ainvention by employing two harmonic generamonic in its group to the highest one in its group.

The invention will be better understood from Athe following detailed description when read in conjunction with the accompanying drawing, in

Fig. 1 shows harmonic distribution curves which would provide the required two groups of frequencies for a carrier communication system of the above-described type.

Fig. 2 shows schematically a magnetic harmonic generator circuit of known type which may be utilized in the system of the invention;

Figs. 3 and 4 show schematically different arrangements of a plurality of harmonic generators of that type for accomplishing the object of the invention;

`Fig. 5 shows curves of harmonic distribution obtainable with the systems of Figs. 3 and 4; and

Fig. 6 shows curves comparing the power eiliciency of the systems of the invention as shown in Figs. 3 and 4 with that of the prior art system of Fig. 2.

described type is to make the harmonic distribution of a single harmonic generator fall off slowly enough to include both groups at the desired power levels. Asshown in the solid line curve of Fig. 1, the harmonic distribution of such a generator would start out atk a power level Wo: for the lowest frequency in the lower frequency group, decrease to a power level W01 at the higest freguency ,f1 in that group, and decrease further to the power level Wo: at the highest frequency f; in the auxiliary high frequency carrier group. Such a harmonic distribution may be obtained with a magnetic harmonic generator such as disclosed in L. R. Wrathall Patent 2,117,752, issued May 17, 1938, the circuit of which is shown in Fig. v2. As shown, that harmonic generator includes a source l of sinusoidal waves of the fundamental frequency f, a primary circuit 2 tuned to that frequency, comprising the linear inductance element *3, the capacitor 4 and the non-linear inductance I, which may be a ,saturable' magnetic core coil, connected in series 25` across the source l, and a secondary circuit 6 comprising the highlyresistive impedance 1 and the capacitor l connected in series across the non-linear'inductance 5. In the manner explained in the aforementioned patent, such a generator with proper relative proportioning of the circuit elements may be`made to produce in the resistance element l an impulse wave containing a large number of odd harmonics of the fundamental frequency f, which over a wide frequency range will have appreciable power level gradually decreasing from the lowest frequency to the highest frequency in that range. v

Another way to obtain the desired two groups of frequencies, which is more eillcient under certain conditions given below than the use of the single harmoniclgenerator for the purpose, is to employ two harmonic generators with harmonic distributions as shown in the curves (1f-Fig. 5.

In one such arrangement in accordance with the invention, shown in Fig. 3, twoseparate harmonic generators A and B of the known type illustrated in Fig. 2 are supplied in parallel from the same base frequency source i. The circuit elements of the harmonic generator A in the y system of Fig. 3 would be properly proportioned so that it supplies a band of harmonics of the frequencies and power levels required for the l lower frequency group of carriers in the referredto carrier supply system, and the circuit elements of the harmonic generator B of the system of Fig. 3 would be properly proportioned to provide a band of harmonics of the frequencies and power levels required for the higher frequency carrier group in that system. As shown by curve A of Fig. 5, the generator A would be designed to supply a flat band of harmonics at the power level Wai up to the highest frequency f1 in the lower carrier frequency group with the amplitude of the harmonics above that frequency falling oif rapidly, and as shown by curve B of Fig. 5 the generator B would be designed to supply a fiat band of harmonics at a lower power level Woe from e. very W harmonic up to the highest frequency f2 in the higher frequency carrier group with the amplitude of higher frequency harmonics falling off rapidly.

Unless it were possible to obtain a harmonic distribution as shown by the dashed line of Fig. 1 from a single harmonic generator,v the most efficient way of supplying the higher frequency carrier group would be with a generator having a harmonic distribution such as shown by the dashed line C in Fig. 5 in which power would not be wasted at the low frequencies. This alternative harmonic distribution for the higher group of carrier frequencies may also be readily obtained by proper relative proportioning of the circuit elements of harmonic generator B in the system of Fig. 3, and by adding an inductance in series with C2.

The total power required for producing the required harmonic distribution for the two groups of carrier frequencies in the case of a single generator and the two generator system may be readily calculated as follows:

For the first case, that is the case of the use of the single harmonic generator as shown in Fig. 2, a distribution with k small (1min/.RZC where Le is the saturated inductance of the non-linear coil) is used, since `this gives the smallest slope over the widest band of frequencies. This distriu bution is represented by W03 Was .r "i" Hagiwara W waarnaar (1 to determine Wo and pCaRa, where m and m are the harmonic numbers corresponding to fr and f2. The quantity pCaRa may be deduced from Equation l. We also have that the total power in this spectrum is :j: Wea We? I 4 pCaRS which we rind by use of the above relations is t -1 1r Bia This shows that the above conditions cannot be satisiied when &2 Wos"i2 because the distribution for k=0 is not steep value of 7c 0 must be used and under this condition no simple expressions can be given.

For the other case where two generators are used (Fig. 3 or 4) we choose npCR=1.0 at the highest frequency in the particular band. Thus 1 d 1 PCiRrnl an I'CzRs-n2 Then the total powers in these distributions are `The total power developed in this case is then W.,+W.,= n.wm+Mw...) 5)

The ratio of total powers in the two cases is 'H22 (FFI) 1 EL@ lha LV2) W02 1 1+7l1 W02 This ratio is plotted in Fig. 6 as a function of m/ni=f2/fi for several values of the ratio Wol/W02.

It is necessary to use k=0 for the distribution of Fig. 1 for the values shown bythe curves of Fig. 6. For other values, determined by the distribution curve can be passed through the two required points in more than one way depending on the value of k, and thus there is not a unique value for the total power.

Thus there is an increase in eiiiciency by using the two generators, which increases with the frequency separation of the two bands. For example, if the ratio of highest frequenciesfz/fi is 8, the power required with two generators is about l'f2/, the power required with a. single generator.

-mary circuit for the two generators A and B connected across the source I and tuned to the fundamental frequency ,f supplied by that source,

comprises the non-linear inductances 5, 5' and a single linear inductance element 3' and a single capacitor 4' in series, the other elements of the two generators A and B being arranged in the same way as in Fig. 3. By proper relative proportioning of the circuit elements of Fig. 4 harmonic distribution characteristics as shown in Fig. 5 may also be attained.

Any harmonic generators which will provide the harmonic distribution characteristics shown in Fig. 5 may be employed in place of the particular magnetic harmonic generators A and B illustrated in the systems of Figs. 3 and 4. For example, a gas-tube harmonic generator of the type disclosed in my Patent 2,174,165 issued September 26, 1939, may be employed in place of each of the generators if their circuit elements aaimsa are suitably proportioned to give the required harmonic distribution curves as shown in Fig. 5. Other modifications of the circuits illustrated and described which are within the spirit and scope of the invention will occur to persons skilled in the art.

What is claimed is:

1. A system for supplying efficiently one group of frequencies at a desired power level and a second group of frequencies considerably higher than those of said one group at an appreciable but lower power level, all frequencies in `both groups being harmonics of the same fundamental frequency, comprising two harmonic generators both controlled from the same wave source of said fundamental frequency, means for causing one of said harmonic generators to produce a band of harmonics of said fundamental frequency having substantially said desired power level over the frequency range of said one group and means for causing the other harmonic generator to-produce ,a band of harmonics of said fundamental frequency having said appreciable but lower power level over the frequency range of said second group.

2. The system of claim 1, in which said harmonic generators are caused to respectively produce a band of harmonics of uniform power level extending from the lowest frequency in said one group to the highest frequency in a different one of said groups.

3. The system of claim l, in which one of said generators is caused to produce a band of harmonies of said fundamental frequency having uniform power over a range extending from the lowest frequency in said one group to the highest frequency in said one group and the second generator is caused to produce a band of harmonics of uniform power over a range extending from the lowest frequency in said second group to the highest frequency in said second group.

4. A system for efficiently supplying carrier waves in a carrier communication system employing a basic group of carriers and an auxiliary group of carriers of frequencies considerably higher than those of the basic group, all frequencies being harmonics of the same base frequency, comprising two harmonic generators, a common source of waves of said base frequency for controlling both generators, and means for causing said generators to respectively supply a band of harmonics of a desired uniform power level over the frequency range of said basic group, and of a desired lower uniform power level over the frequency range of said auxiliary group.

Cil

5. The system of claim 1 in which scid gcnerators are of the saturabls magnetic core coil type, the different frequency ranges of desired power level being obtained by different prop.rtioning oi.' the circuit constants of the two generators.

6. The system of claim 1 in which said harmonic generators include a common primary circuit connected across said source and tuned to the fundamental frequency thereof, comprising two non-linear inductances, a linear inductance and a capacitor in series, individual secondary circuits each including a. resistive impedance and a capacitor connected in series across a different one of said non-linear inductances, the circuit elements of the two harmonic generators being respectively properly proportioned to produce in the secondary circuit of each generator an impulse wave having the harmonic distribution required for a different one of said groups, and means for picking olf the produced harmonic Wave from the secondary circuit of each generator.

7. A system for supplying efiiciently one group of frequencies at a desired power level and a second group of frequencies considerably higher than those of said one group at an appreciable but lower power level, all frequencies in both groups being harmonics of the same fundamental frequency, said system comprising a single source of sinusoidal waves of said fundamental frequency and two harmonic generators each comprising a non-linear inductance, a primary circuit including said non-linear inductance, tuned to said fundamental frequency, connected across said source, a secondary circuit including a highly resistive impedance and a capacitor in series, connected across said non-linear inductance, the non-linear inductance and the elements in the secondary circuit of .one harmonic generator being relatively proportioned so that the generator produces a' band of harmonics of said fundamental frequency having substantially said desired power level over the frequency range of said one group, the non-linear inductance and the elements in the secondary circuit of the other harmonic generator being differently relatively proportioned so that the latter` generator produces a band of harmonics of said fundamental frequency having said appreciable but lower power level over the frequency range of said second group, and means for taking off the produced harmonics from the secondary circuit of each harmonic generator,

EUGENE PETERSON. 

